Common names for the Lawnmower Blenny include Algae Blenny, Sailfin Blenny, Jewelled Blenny, Rockskipper Blenny, Rock Blenny & Rockhopper Blenny.

Lawnmower Blenny
Lawnmower Blenny

Like most Blennies, these fish will spend their day perched on rocks, eating away at the microalgae and detritus that builds up in your aquarium. They are not really open swimmers and will spend most of their day either on the rocks, on the sandbed or hiding in caves.

Some people may consider these fish quite plain looking in comparison to some of the more colourful fish species available in saltwater aquariums. They are a mottled brown colour, but they have interesting spikes and oversized eyes that make them a bit more interesting to look at. What they may lack in colour, they certainly make up for in personality.

Tank Requirements & Facts

Sailfin Blenny
Sailfin Blenny
  • Minimum tank size: 30 Gallon (136 Litres)
  • Prone to disease: No
  • Beginner Compatible: Yes
  • Adult Size: 5 inches (12.7cm)
  • Reef Compatible: Yes
  • Predator Tank Compatible: No
  • Care Level: Easy
  • pH: 8.1 to 8.4
  • Temperature: 22°C to 27°C
  • Preferred Tank Level: Bottom
  • Lots of hiding places required
  • Lots of rock for varied algae growth
  • Number to a tank: One to be kept per tank. They will fight with another member of the Blenny family that has a similar shaped body to them or the same colouring
  • They are not always compatible with sand sifting gobies

Feeding

  • These are herbivores
  • They are not overly aggressive eaters
  • They will graze on Nori that has fallen from a clip
  • They love sinking algae pellets
  • Flaked foods are sometimes accepted

Acclimatisation

Place your fish in the bucket and then drip acclimate for about 45 minutes at a rate of 3 drips per second. This should bring the fishes water parameters in line with your tanks parameters.

Once your fish has been drip acclimated, catch the fish with a net and place it gently into your tank. Do not put any of the water the fish originally came in, into your tank.

Can I Keep A Lawnmower Blenny With A Sandsifting Goby?

Chalk Goby - White with Electric Blue Dots on Cheek
Chalk Goby – White with Electric Blue Dots on Cheek

These fish are peaceful, and won’t bother 99% of the inhabitants of your aquarium, they even leave your clean up crew & corals alone.

But, they will not tolerate another fish that is either the same colour or shape as them. The sandsifting gobies can have a similar body shape and they will fight. Blennies are particularly fond of picking on the smaller gobies.

This doesn’t mean you can’t keep a sailfin blenny with a sandsifting goby successfully. It just means you have to make sure you pick a goby that is not the same colour or body shape. Speaking from experience, a chalk goby works well. Gobies to avoid would include watchman gobies, pink spotte shrimp gobies, Y-Bar gobies, orange spot gobies & fan shrimp gobies.

Rockhopper Blenny
Rockhopper Blenny

 Personal Review

I was so dubious about getting one of these, I didn’t think my tank was established enough for it. By this, I mean there wasn’t enough algae growth. I had also read about them not being great with sandsifting fish, and I already had my chalk goby.

He is not the most colourful fish in my tank, but he makes up for it with his personality! He is everywhere you look in the tank… in the little caves, on the back wall, hoping along the sand. Whenever I look at my tank, he is out and about just doing his thing. I find myself looking for him first in my tank.

I love how he perches on the rocks, just staring at you to see if you are about to put any food in the tank. He pops out of the holes and caves like a little jack in the box. He is honestly the most amusing fish I have in my aquarium.

As far as aggression goes, I have only ever seen him chase my Goby once. The rest of the time he just keeps himself to himself. I would recommend that everyone who has a big enough tank should get a Lawnmower Blenny!